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PATH FINAL > MI: CNS Infections and Meningitis > Flashcards

MI: CNS Infections and Meningitis Flashcards

(42 cards)

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1
Q

What are the routes of entry into the CNS?

A
  • Haematogenous (e.g. pneumococcus, meningococcus)
  • Direct implantation (e.g. trauma or iatrogenic)
  • Local extension (e.g. from the ear)
  • PNS into CNS (e.g. rabies)
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2
Q

What is the most common route of entry for pathogens?

A

Haematogenous

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3
Q

What are the 4 main clinical syndromes caused by pathogens which successfully invade the CNS

A
  • Meningitis (meninges)
  • Encephalitis (brain)
  • Myelitis (spinal cord)
  • Neurotoxin (CNS and PNS)
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4
Q

Define Meningitis

A

inflammatory of the meninges and CSF

(Meningoencephalitis = infalmmation of teh meninges and brain parenchyma)

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5
Q

How is neurological damage caused in meningitis

A
  • Direct bacterial toxicity
  • Indirect inflammatory response, cytokine release and oedema
  • Shock, seizures and cerebral hypoperfusion
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6
Q

What are the three types of meningitis?

A
  • Acute (hours to days)
  • Chronic (days to weeks)
  • Aseptic (caused by viruses so there is no pus)
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7
Q

Name three organisms that cause acute meningitis.

A
  • Neisseria meningitidis
  • Streptococcus pneumoniae (bimodal distrubution)
  • Haemophilus influenzae
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8
Q

How many serotypes of N. meningitidis are there?

A
  • ≥12 serotypes (90% = A, B, C)

A, B, C, W and Y are vaccinated against

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9
Q

How does N. meningitidis enter the body?

A

Through the nasopharyngeal mucosa in susceptible individuals

NOTE: only 1% of carriers of N. meningitidis have pathogenic strains

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10
Q

What types of rashes can children develop if infected by N. Meningitidis

A

Resulting in:
* non-blanching rash (80% of children)
* Maculopapular rash (13% of children)
* No rash (7%)

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11
Q

How long does N. meningitidis take to cause infection?

A

< 10 days

50% will develop meningitis
7-10% will develop septicaemia
40% will develop both

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12
Q

What are the four processess that occur in septicaemia?

A
  • Capillary leak - albumin and other plasma proteins lead to hypovolaemia
  • Coagulopathy - leads to bleeding and thrombosis, endothelial injury results in platelet release reactions, the protein C pathway and plasma anticoagulants are affected
  • Metabolic deragnement - particularly acidosis
  • Myocardial failure - and multi-organ failure
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13
Q

List some other, rarer bacterial causes of acute meningitis.

A
  • Listeria monocytogenes
  • Group B Streptococcus
  • Escherichia coli
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14
Q

Outline the presentaiton of TB meningitis.

A
  • TB meningitis is a type of chronic meningitis as takes weeks to present
  • Similar presentation to acute meningitis
  • Tends to occur in immunocompromised patients
  • Involves the meninges and basal cisterns of the brain and spinal cord - as is the case with most chronic meningitis cases.
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15
Q

List some complications of TB meningitis.

A
  • Tuberculous granulomas
  • Tuberculous abscesses
  • Cerebritis
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16
Q

What is a typical CT/MRI feature of TB meningitis?

A

Thickening of meninges and basal cisterns of brain and spinal cord

Dilatation of ventricles

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17
Q

What is the most common infections of the CNS?

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A

Aseptic meningitis

18
Q

What is aseptic meningitis?

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A

Meningitis that is caused by viruses and is not purulent

19
Q

What are the most common causative organisms in aseptic meningitis?

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A

Coxsackie group B viruses

Echoviruses (HSV-2 commonest in UK)

20
Q

Clinical Presentation of Aseptic meningitis

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A

Commonly affected age group: < 1 year

  • Non-specific rash accompanying headache, stiff neck, photophobia sx, buldging fontanelle
  • normally self-resolving after 1-2 weeks
21
Q

How is encephalitis transmitted?

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A

Haematogenous (either person-to-person or through vectors such as mosquitoes)

22
Q

List some viruses that cause encephalitis.

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A
  • Mumps
  • Measles
  • Enteroviruses
  • Herpes viruses
23
Q

What is becoming a leading cause of encephalitis worldwide?

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A

West Nile virus

NOTE: this is transmitted by mosquitoes and birds

24
Q

Which bacterium is associated with causing encephalitis?

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A

Listeria monocytogenes

25
What is toxoplasmosis and how is it spread?
* Obligate intracellular parasite * Spread via oral, transplacental or organ transplant route
26
How do bacteria that cause brain abscesses tend to spread?
Direct extension (e.g. from otitis media, mastoiditis or paranasal sinuses)
27
List some organisms that can cause brain abscesses.
* Streptococci * Staphylococci * Gram-negative organisms (mainly in neonates) * TB, Fungi, Parasites *note in order of commonest*
28
How can brain abscesses result in death
Pressure-related issues
29
Name a common spinal infection.
Pyogenic vertebral osteomyelitis - a common vertebral infection (e.g. staph or strep)
30
How can pyogenic vertebral osteomyelitis spread?
Direct open spinal trauma from infections in adjacent structures
31
What are some long-term consequences of pyogenic vertebral osteomyelitis if left untreated?
* Permanent neurologic defects * Significant spinal deformity * Death
32
List some risk factors for pyogenic vertebral osteomyelitis.
* Age * IVDU * Long-term systemic steroids * Diabetes mellitus * Organ transplantation * Cancer * Malnutrition
33
Compare the use of MRI and CT in CNS infections.
MRI is better than CT at detecting parenchymal abnormalities such as abscesses and infarctions
34
List some other useful tests for suspected meningitis.
* CSF Study * Blood culture * Throat swab * Blood PCR * Sputum culture * Urine culture
35
What studies can be done with CSF?
* Colour/clarity * Cell counts * Chemistry (protein and glucose) * Stains (Gram, auramine, Inda Ink etc.) * Cultures * PCR
36
Describe the typical CSF analysis results of: 1. Bacterial meningitis 2. Aseptic meningitis 3. Tuberculous meningitis
**Bacterial meningitis:** * Turbid * High polymorphs * High protein * Low glucose **Aseptic meningitis:** * Clear * High lymphocytes * High protein * Normal glucose **Tuberculous meningitis:** * Clear * High lymphocytes * High protein * Low glucose
37
Describe the Gram-stain and microscopic appearance of: 1. *S. pneumonia* 2. *N.meningitidis* 3. *L. monocytogenes* 4. TB 5. *Cryptococcus*
1. ***S. pneumonia*** = Gram-positive alpha-haemolytic diplococci 2. ***N.meningitidis*** = Gram-negative non-haemolytic diplococci 3. ***L. monocytogenes*** = Gram-positive rods 4. **TB** = Stains positively with Ziehl-Neelsen (red and blue) 5. ***Cryptococcus*** = Stains positively with India Ink (appears like an orbit - yeast in the middle with a capsule around the outside)
38
What is another key clinical feature of Cryptococcal meningitis?
High opening pressure
39
List some limitations of diagnositcs in menigitis.
* MRI oedema pattern may not differentiate between tumour or stroke or vasculitis in some patients * Serology may not be useful in the early stages of infection * Difficulties obtaining CSF * PCR techniques are expensive
40
What is the treatment for anyone with suspected meningitis?
* Ceftriaxone 2g IV BD * If \> 50 years or immunocompromised or neonate= amoxicillin 2 g IV 4 hourly NOTE: this is because ceftriaxone does NOT cover *Listeria*
41
What is the treatment for anyone with suspected meningo-encephalitis?
* Aciclovir 10 mg/kg IV TDS * Ceftriaxone 2 g IV BD * If \> 50 years or immunocompromised = amoxicillin 2 g IV 4 hourly
42
Name the specific therapy for meningitis caused by: 1. *S. pneumoniae* 2. *N. meningitidis* 3. *H. influenzae* 4. Group B *Streptococcus* 5. *Listeria* 6. Gram-negative bacilli 7. *Pseudomonas*
**1. *S. pneumoniae* =** Pen G 18-24 mu/day **2. *N. meningitidis*** = Ceftriaxone 4 g/day **3. *H. influenzae*** = Cefotaxime 12 g/day **4. Group B *Streptococcus*** = Pen G 18-24 mu/day **5. *Listeria*** = Ampicillin 12 g/day **6. Gram-negative bacilli** = Cefotaxime 12 g/day **7. *Pseudomonas*** = Meropenem 6 g/day

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